1. Field
One or more embodiments relate to laser-induced ultrasonic wave apparatuses and methods, including laser-induced ultrasonic wave apparatuses and methods generating one or more images.
2. Description of the Related Art
When a laser beam irradiates a liquid material or a solid material, the liquid or solid materials respectively absorbs light energy, and thus, heat energy becomes instantly generated. This generation of heat also generates acoustic waves, e.g., ultrasonic waves, due to a thermoelastic phenomenon. Here, respective absorptances and thermoelastic coefficients for different materials may also vary with respect to light wavelengths of light energy irradiating the respective materials. Thus, when different materials are irradiated with the same light energy, ultrasonic waves of different pressure magnitudes may be generated by the respectively different materials. Such ultrasonic waves that may be generated can be used for analysis of select materials, non-destructive diagnoses, photoacoustic tomography, etc.
Particularly, photoacoustic tomography may embody functional images that may be helpful for diagnoses that rely on a functional analysis of the different absorptances of tissues within the human body according to the light wavelengths of the light energy irradiating such tissues.
However, though such respective functional images or photoacoustic images may be generated, e.g., when a particular tissue is irradiated by light energy, an acoustic image or anatomical image for acoustical analysis is not generated based on the light energy irradiating the particular tissue or multiple tissues because pressure magnitudes of acoustic waves generated from the irradiation of only select tissues may be measurable, reliable, or available for acoustical analysis. This is because most materials making up the human body have low light energy absorptances, and thus, except for particular tissues like blood vessels that have relatively larger light energy absorptances, the pressure magnitudes of acoustic waves generated for such low light energy absorptance tissues are relatively very small.
Accordingly, it is difficult to distinguish between different low light energy absorptance tissues when they generate respectively small pressure magnitude acoustic waves, especially considering detection resolutions and potential substantial similarities between the relatively smaller pressure magnitude acoustic waves generated by different low light energy absorptance tissues. Therefore, it is difficult to generate anatomical images based on the thermoelastic phenomenon that can be used in an acoustical diagnosis, e.g., an ultrasonic image based diagnosis, so only functional images or photoacoustic images are generated by light energy irradiated, e.g., direct irradiation, to tissues in a human body.
Therefore, for a diagnosis that is based on both the functional analysis and the anatomical analysis, it is necessary to independently, i.e., using different acoustic generating devices or elements and techniques, generate the photoacoustic tomography image for the functional analysis and an anatomical image for anatomical analysis.
The anatomical image is typically based on acoustic waves, e.g., an ultrasound ultrasonic waves, generated by a piezoelectric device that are transmitted to, and reflected from, tissues in the human body. The anatomical image can be a typical ultrasound image. However, when piezoelectric devices are used to generate the ultrasonic waves, characteristics of the generated ultrasonic waves, such as center frequency and bandwidth, are fixed because a center frequency and bandwidth of a generated ultrasonic wave are defined by the thickness of the piezoelectric device, which is fixed. Accordingly, separate piezoelectric device probes are necessary for generating respective ultrasonic waves with different center frequencies and bandwidths, e.g., for respectively different diagnosis regions.